[Federal Register Volume 79, Number 91 (Monday, May 12, 2014)]
[Proposed Rules]
[Pages 26901-26905]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-09929]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2013-0766; Directorate Identifier 2013-NE-26-AD]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney Canada Corp. Turboprop 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (NPRM); request for 
comments.

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SUMMARY: We are revising an earlier proposed airworthiness directive 
(AD) for all Pratt & Whitney Canada Corp. (P&WC) PT6A-114 and PT6A-114A 
turboprop engines. The NPRM proposed to require initial and repetitive 
borescope inspections (BSIs) of compressor turbine (CT) blades, and the 
removal from service of blades that fail inspection. The NPRM was 
prompted by several incidents of CT blade failure, causing power loss 
and in-flight shutdown of the engine resulting in four fatalities. This 
action revises the NPRM by adding a mandatory terminating action. We 
are proposing this supplemental NPRM (SNPRM) to prevent failure of CT 
blades, which could lead to damage to the engine and damage to the 
airplane. Since these actions impose an additional burden over that 
proposed in the NPRM, we are reopening the comment period to allow the 
public the chance to comment on this proposed change.

DATES: We must receive comments on this SNPRM by June 26, 2014.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE., Washington, DC 20590.
     Hand Delivery: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    For service information identified in this proposed AD, contact 
Pratt & Whitney Canada Corp., 1000 Marie-Victorin, Longueuil, Quebec, 
Canada, J4G 1A1; phone: 800-268-8000; fax: 450-647-2888; Internet: 
www.pwc.ca. You may view this service information at the FAA, Engine & 
Propeller Directorate, 12 New England Executive Park, Burlington, MA. 
For information on the availability of this material at the FAA, call 
781-238-7125.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2013-
0766; or in person at the Docket Management Facility between 9 a.m. and 
5 p.m., Monday through Friday, except Federal holidays. The AD docket 
contains this proposed AD, the Transport Canada Civil Aviation (TCCA) 
AD, the regulatory evaluation, any comments received, and other

[[Page 26902]]

information. The address for the Docket Office (phone: 800-647-5527) is 
in the ADDRESSES section. Comments will be available in the AD docket 
shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Robert Morlath, Aerospace Engineer, 
Engine Certification Office, FAA, Engine & Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803; phone: 781-238-7154; 
fax: 781-238-7199; email: [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2013-0766; 
Directorate Identifier 2013-NE-26-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed AD because of those comments.
    We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    We issued an NPRM to amend 14 CFR part 39 by adding an AD that 
would apply to all P&WC PT6A-114 and PT6A-114A turboprop engines. The 
NPRM published in the Federal Register on October 29, 2013 (78 FR 
64421). The NPRM proposed to require initial and repetitive BSIs of CT 
blades, and the removal from service of blades that fail inspection.

Actions Since Previous NPRM Was Issued

    Since we issued the NPRM, we received additional information as a 
result of comment responses and as part of an ongoing investigation.

Comments

    We gave the public the opportunity to participate in developing 
this AD. We considered the comments received.

Agreement With the Proposed AD

    The National Transportation Safety Board (NTSB) and Hawkins Aero 
agreed with the need for the AD action.

Request To Harmonize

    TCCA requested that the Compliance section of this AD be revised to 
mandate that operators replace pre-P&WC Service Bulletin (SB) No. PT6A-
72-1669 CT blades with single crystal CT blades within the next 36 
months. TCCA's AD CF 2013-21R1 mandates that operators replace all CT 
blades with new part number (P/N) single crystal CT blades within 36 
months after the effective date of the AD to address the unsafe 
condition of CT blade failures due to creep. The NPRM does not mandate 
that new P/N single crystal CT blades be installed within a particular 
period of time. TCCA requested that we revise the FAA AD to better 
address the unsafe condition.
    We agree. We changed the Compliance paragraph to require that all 
CT blades be replaced with single crystal CT blades within 36 months 
after the effective date of this AD.

Request To Remove Mandatory Upgrade

    Hawkins Aero and an individual commenter requested that the AD not 
require operators to upgrade to single crystal CT blades. Hawkins Aero 
stated that based on knowledge of previously conducted metallurgical 
examinations, certain operators experience higher levels of CT blade 
deterioration based on operating practices. The other commenter stated 
that low utilization operators may face a heavy economic burden in 
order to upgrade to the new single crystal CT blades.
    We partially agree. We disagree with allowing certain operators to 
not upgrade to single crystal CT blades because CT blade failure due to 
creep is a significant problem for this type design, and the unsafe 
condition identified in this AD must be corrected. We did not change 
the requirement to replace the CT blades. We agree that mandating the 
installation of single crystal CT blades will impose a significant 
economic burden on low utilization operators. As such, we are re-
opening the comment period for this AD to allow the public the chance 
to comment on the proposed changes. The additional economic costs for 
low utilization operators are included in the Costs of Compliance.

Request To Change Borescope Inspection Requirements

    The same individual commenter requested a review and modification 
of the compliance time for the initial and repetitive BSIs for low-
utilization operators. The commenter justified this request by stating 
that, ``Since the vast majority of the 114A fleet is utilized in the 
relatively high utilization environment of commercial operation, based 
on an assumption of 500 hours annual utilization, the repetitive BSIs 
would be done on an annual basis''.
    We do not agree. The creep condition addressed by this proposed AD 
is related to time in operation at high temperature and high power 
settings, not calendar time. We did not change the compliance time.

Request To Change Definitions Paragraph

    Hawkins Aero requested that we revise the Definitions paragraph to 
include specific original equipment manufacturer and parts manufacturer 
approval (PMA) P/Ns. The justification for this request is that the 
proposed AD does not specifically identify pre- and post-SB No. PT6A-
72-1669 P/Ns and does not list PMA P/Ns.
    We partially agree. We agree that P/N identification is necessary. 
We identified what P/Ns can be installed during the compliance period 
and what P/Ns must be installed prior to the end of the 36-month 
compliance period. We disagree with listing all potential original 
equipment manufacturer and PMA P/Ns. We deleted the Definitions 
paragraph and expanded the Compliance paragraph to identify eligible P/
Ns.

Request To Include Two-Blade Metallurgical Examination

    TCCA and Hawkins Aero requested that the Compliance paragraph be 
changed to require operators to perform a two-blade metallurgical 
examination at each hot section interval (HSI). The reason for this 
request is that the P&WC maintenance manual recommends, and the TCCA AD 
currently requires, that operators perform a metallurgical evaluation 
of two CT blades at each HSI in lieu of replacing the entire set. Based 
on the deterioration of the micro-structure observed in the two blade 
sample, a determination is made as to whether the remaining CT blades 
can continue in service. TCCA also requested that we revise the 
Applicability paragraph of the AD to clearly state that the CT blades 
be replaced or undergo metallurgical evaluation, repetitively, at each 
HSI. TCCA stated that the NPRM did not clearly state whether the 
evaluation was a one-time or a repetitive requirement and that without 
requiring the evaluation be made at each HSI our AD does not meet the 
basic intent of their AD, which was to detect the impending failure of 
the CT blades as a result of creep on all engines moving forward.

[[Page 26903]]

    We partially agree. We agree with allowing operators to perform the 
metallurgical examination instead of replacing the entire set of CT 
blades at each HSI because the metallurgical evaluation is an approved 
method for determining if installed CT blades support continued safe 
operation. We also agree with repetitive replacement of CT blades at 
each HSI.
    We do not agree with requiring operators to perform the 
metallurgical examination at each HSI because new CT blades can be 
installed. We have determined that either performing the metallurgical 
examination or installing new CT blades will provide an acceptable 
level of safety. We changed the Compliance paragraphs to allow 
operators to perform the metallurgical examination or replace the 
entire set of CT blades with new blades at each HSI.

Request Harmonization of Compliance Times

    The NTSB requested that the difference in compliance time for the 
BSI between the NPRM (78 FR 64421, October 29, 2013), the TCCA AD, and 
the P&WC SB be explained in further detail. The NTSB stated that P&WC 
SB No. PT6A-72-1669, Revision 9, dated June 28, 2013, includes a re-
inspection interval for the repetitive BSIs of 400 hours time-in-
service (TIS) while the NPRM and the TCCA AD specify 500 hours TIS.
    We do not agree. The 500 hour TIS inspection interval addresses the 
unsafe condition by providing an acceptable level of safety. We did not 
change the AD.

Request To Add Repetitive Inspections

    Hawkins Aero requested that the compliance paragraph of the 
proposed AD be revised to include repetitive BSIs and HSI metallurgical 
inspections for single crystal CT blades. The reason for this request 
is that the commenter does not believe that the repetitive inspections 
should be relaxed for the single crystal CT blades until more data can 
be gathered about their performance. Reference was made to an engine 
failure that occurred on an engine with single crystal CT blades as 
evidence that while the design is an improvement on previous blade 
versions they are not immune to failure.
    We do not agree with mandating that the new CT blades be subjected 
to an inspection program designed for a different blade design and P/N. 
The investigation into single crystal CT blade failures has not been 
completed and therefore, the need for additional corrective action has 
not been determined. We did not change the AD.

Request To Add Additional Inspection

    Hawkins Aero requested that the Compliance paragraph be changed to 
include platform gap inspections as well as installation instructions 
to ensure the proper platform gap is achieved during HSI for P&WC 
single crystal CT blades, P/N 3072791-01. This change was justified 
because single crystal CT blades, P/N 3072791-01 and P/N 3072791-02, 
have different blade platform gap tolerances. The P/N 3072791-01 
tolerances may lead to a smaller gap between blade platforms than on 
the P/N 3072791-02 blades leading to a potential failure of the CT 
blade.
    We do not agree. There have been no unsafe conditions identified 
concerning the platform gap dimensions that would warrant this change. 
We did not change the AD.

Request Revision to Economic Evaluation

    Hawkins Aero requested that the economic evaluation section of the 
AD include foreign-registered products and corresponding revisions to 
the compliance section. This request was justified because accounting 
for foreign-registered products would increase the projected cost for 
the AD; additionally, the commenter recommends that we revise the 
compliance paragraph and include the additional costs for all 
additional actions.
    We partially agree. We agree with revising the Costs of Compliance 
to include any changes that are made to the compliance paragraph. We 
disagree with including foreign-registered products in the Costs of 
Compliance because we do not consider the cost of AD actions for 
foreign-registered products. We changed the AD to account for 
Compliance paragraph changes in the Costs of Compliance.

Request Addition of Cockpit Placard

    Hawkins Aero requested that the Compliance paragraph of the 
proposed AD be revised to include the installation of a placard in the 
cockpit alerting the pilot to various operational limits and re-
iterating warnings from the engine and aircraft Instructions for 
Continued Airworthiness (ICAs). The reason given for this request is 
that the current guidance for pilots and maintenance personnel is not 
sufficient to prevent the aircraft from being operated beyond its 
published limits. Additionally, there are certain procedures that the 
pilots, operators, and maintenance personnel can perform to ensure 
continued safe operation.
    We do not agree. Including instructions for aircraft operation does 
not fall within the guidelines of the AD action. We discussed this 
comment with the appropriate aircraft certification office.

Request Revision to Optional Terminating Action

    Hawkins Aero requested that the Optional Terminating Action 
paragraph be revised to include guidance for operators on whether or 
not to install single crystal CT blades, based on operational history 
and the cost of parts. This request is justified based on historical 
differences between the CT blade deterioration experienced by certain 
operators and the costs of the new CT blades.
    We do not agree. Providing guidance to operators based on blade 
deterioration vs. cost of replacement is contrary to the intent of 
addressing the unsafe condition. We did not change the AD.

Request Revision to Compliance

    Hawkins Aero requested that the Compliance paragraph be revised to 
state that cracked, stretched, sulfidated, or abnormal blades should be 
removed from service. A justification for this request was not 
provided.
    We do not agree. The engine ICA provide data for serviceable limits 
for all engine components. We did not change the AD.

Request Revision to Compliance

    Hawkins Aero requested that the Compliance paragraph be revised to 
provide a recommendation that the repetitive BSIs be scheduled to 
coincide with pre-existing fuel nozzle inspections and to state the 
maximum allowable HSI. The reason for this request is that fuel nozzle 
inspection intervals match mandated BSI intervals. The HSI 
recommendation is 1,800 hours.
    We do not agree. The HSI recommendations are stated in the ICA and 
providing guidance on scheduling of maintenance actions does not 
support an AD action intended to address an unsafe condition in an 
aircraft, aircraft engine, propeller, etc. We did not change the AD.

Request Revision to Compliance

    Hawkins Aero requested that the Compliance paragraph be revised to 
include CT disk and blade inspection intervals and requirements from 
the overhaul manual. The reason for this change is to provide 
background information for operators.
    We do not agree. Restating requirements that are available to

[[Page 26904]]

operators is redundant. We did not change the AD.

FAA's Determination

    We are proposing this SNPRM because we evaluated all the relevant 
information and determined the unsafe condition described previously is 
likely to exist or develop in other products of the same type design. 
Certain changes described above expand the scope of the NPRM (78 FR 
64421, October 29, 2013). As a result, we have determined that it is 
necessary to reopen the comment period to provide additional 
opportunity for the public to comment on this SNPRM.

Proposed Requirements of This SNPRM

    This SNPRM would require accomplishing the actions specified in the 
NPRM, except as discussed under ``Differences Between this SNPRM and 
the Service Information.''

Differences Between This SNPRM and the Service Information

    The service information requires that all operators perform 
metallurgical examinations of the CT blades at HSI while the proposed 
AD allows for either removal of the CT blades from service at HSI or 
performance of the metallurgical examination.

Costs of Compliance

    We estimate that this proposed AD would affect about 300 engines 
installed on airplanes of U.S. registry. We also estimate that it would 
take about 4 hours per engine to perform the required inspection and 8 
hours to perform parts replacement. The average labor rate is $85 per 
hour. Required parts would cost about $59,334 per engine. Based on 
these figures, we estimate the cost of this proposed AD on U.S. 
operators to be $18,106,200.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. ``Subtitle VII: Aviation Programs'' 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701: ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD would not 
have a substantial direct effect on the States, on the relationship 
between the national Government and the States, or on the distribution 
of power and responsibilities among the various levels of government.
    For the reasons discussed above, I certify this proposed 
regulation:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Is not a ``significant rule'' under the DOT Regulatory Policies 
and Procedures (44 FR 11034, February 26, 1979),
    (3) Will not affect intrastate aviation in Alaskato the extent that 
it justifies making a regulatory distinction, and
    (4) Will not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec.  39.13  [Amended]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive (AD):

Pratt & Whitney Canada Corp.: Docket No. FAA-2013-0766; Directorate 
Identifier 2013-NE-26-AD.

(a) Comments Due Date

    We must receive comments by June 26, 2014.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all Pratt & Whitney Canada Corp. (P&WC) PT6A-
114 and PT6A-114A turboprop engines.

(d) Unsafe Condition

    This AD was prompted by several incidents of compressor turbine 
(CT) blade failure, causing power loss and in-flight shutdown of the 
engine resulting in four fatalities. We are issuing this AD to 
prevent failure of CT blades, which could lead to damage to the 
engine and damage to the airplane.

(e) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.
    (1) For engines that have CT blades installed other than CT 
blades, part numbers (P/Ns) 3072791-01 or 3072791-02, perform the 
following actions:
    (i) Within 150 operating hours after the effective date of this 
AD, perform a borescope inspection (BSI) of CT blades for engines 
with 500 or more hours time-since-new that have not been previously 
inspected or time-since-last-inspection (TSLI).
    (ii) Thereafter, repeat the inspection in paragraph (e)(1)(i) of 
this AD within 500 flight hours TSLI.
    (iii) During the next hot section inspection (HSI) after the 
effective date of this AD, and each HSI thereafter, replace the 
complete set of CT blades with any of the following:
    (A) New CT blades;
    (B) CT blades that have passed a two-blade metallurgical 
examination in accordance with paragraph 3.B. of P&WC Service 
Bulletin (SB) No. PT6A-72-1669, Revision 9, dated June 28, 2013; or
    (C) P&WC single crystal CT blades, P/Ns 3072791-01 or 3072791-
02.
    (2) Reserved.

(f) Mandatory Terminating Action

    Within 36 months after the effective date of this AD, replace 
the complete set of CT blades with single crystal CT blades, P/Ns 
3072791-01 or 3072791-02.

(g) Credit for Previous Action

    If you performed P&WC SB No. PT6A-72-1669, Revision 9, dated 
June 28, 2013, or earlier versions, you have met the initial 
inspection requirements of this AD. However, you must still comply 
with the repetitive inspection requirement of paragraph (e)(1)(ii) 
of this AD.

(h) Alternative Methods of Compliance (AMOCs)

    The Manager, Engine Certification Office, FAA, may approve AMOCs 
to this AD. Use the procedures found in 14 CFR 39.19 to make your 
request.

(i) Related Information

    (1) For more information about this AD, contact Robert Morlath, 
Aerospace Engineer, Engine Certification Office, FAA, Engine & 
Propeller Directorate, 12 New England Executive Park, Burlington, MA 
01803; phone: 781-238-7154; fax: 781-238-7199; email: 
[email protected].
    (2) Refer to Transport Canada Civil Aviation AD CF-2013-21R1, 
dated October 31, 2013, for more information. You may examine AD CF-
2013-21R1 in the AD docket on the Internet at http://

[[Page 26905]]

www.regulations.gov/!documentDetail;D=FAA-2013-0766-0002.
    (3) For service information identified in this AD, contact Pratt 
& Whitney Canada Corp., 1000 Marie-Victorin, Longueuil, Quebec, 
Canada, J4G 1A1; phone: 800-268-8000; fax: 450-647-2888; Internet: 
www.pwc.ca.
    (4) You may view this service information at the FAA, Engine & 
Propeller Directorate, 12 New England Executive Park, Burlington, 
MA. For information on the availability of this material at the FAA, 
call 781-238-7125.

    Issued in Burlington, Massachusetts, on April 18, 2014.
Colleen M. D'Alessandro,
Assistant Directorate Manager, Engine & Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 2014-09929 Filed 5-9-14; 8:45 am]
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